High power rf window protective device



June 2, 1970 WACHTENHEIM- 3,51

I HIGH POWER RF WINDOW PROTECTIVE DEVICE V Filed Sept. 7, 1967 HY TO POWER TUBE NO-GO CIRCUIT IMP-P TO I3 SYSTEM WAVEGUIDE AND ANTENNA INVENTOR,

EIM.

ARTHUR I. WACHTENH y) a. 1%

AGENT 8 ATTORNEYS.

U.S. Cl. 31751 3 Claims ABSTRACT OF THE DISCLOSURE An electronic-vacuum high power RF window protective device which includes an evacuated section of waveguide terminated at each end by a vacuum tight window one of which is coupled to a high power tube. B'razed to the top surface of the waveguide is a capped cylindrical container through which there is extended a filament wire which is connected in series with a go-no-go circuit that controls the operative voltages of the high power tube. A high intensity are will first destroy the window in the electronic vacuum device thereby causing an air leak which in turn will cause the filament to burn out. The burned out filament will cause an open circuit thereby turning off the high power in the line and squelching the arc.

The invention described herein may be manufactured, used, and licensed by or for the 'Govemment for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to high power radiation systems and more particularly to apparatus for protecting the components in such systems against damage due to arcing.

One of the major problems incident to the operation of high power microwave systems, and particularly high power continuous wave transmitters or microwave generators resides in the fact that after voltage breakdown arcs form, they invariable travel along the guide towards the source of RF power, destroying in its passage such obstacles as dielectric windows. Where the source of power is a generator tube such as a klystron, the arc will destroy its windows thereby resulting in loss of vacuum and consequential destruction of the tube. While arc destroyer systems available today rely on optical electronic or solely electronic devices, these methods are not completely effective in protecting high power windows.

SUMMARY OF THE INVENTION vide an arc detector protective device which may double as a replaceable high power window.

In accordance with the present invention there is provided an apparatus for protecting a high power tube in a waveguide system including for insertion in the system a section of evacuated waveguide terminated by sealed RF windows with one of the RF windows coupled to the output of the high power tube. The high power tube is normally activated by a source of operating voltages. Included further is a protective response means within the waveguide section and in circuit with the operating voltage source. The protective response means is responsive to an arc discharge circuit in the waveguide system such that the operating voltage source is disconnected from the high power tube to render it inactive.

United States Patent O 3,515,946 Patented June 2, 1970 BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description taken in connection with the figure of the accompanying drawing which is a sectionalized perspective view partially schematic of one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, at 12 there is' shown a high power generator tube such as a klystron having an output window 14. Attached to window 14 is a section of evacuated waveguide section 16 which couples the output power of klystron 12 to a conventional waveguide system and antenna. The waveguide section 16 is the electronic vacuum device which will protect the klystron output window 14 from destruction by an arc which initiates somewhere in the antenna waveguide system 13 and travels towards the high power generator source 12. As shown, waveguide section 16 is terminated by end windows 18 and 20 toform an evacuated structure. The vacuum tight windows are brazed into respective flanges 22 and 24 in the conventional manner. A filament wire 26 extends through the top wall of waveguide section 16 and is maintained in position by means of a suitable holder 28 which is provided with a cap 30 through which the ends of filament wire 26 may extend. The type of filament used is similar to those in devices such as miniature entertainment vacuum tubes, pilot bulbs or any vacuum device requiring a heater element. After the filament and cap are in place, the entire waveguide section 16 is evacuated. WLhen waveguide section 16 is thus evacuated, a suitable potential source 31 is connected in circuit with the filament wire 26 which in turn is connected in series with a go-no-go circuit 32 that controls the application of operating voltages to high power tube 12. Although the high power source has been shown as a klystron, it is to be understood that the invention is not limited thereto and other high power sources such as travelling wave tubes may also be utilized.

In operation, if an arc develops in the antenna waveguide system 13, it will move toward the high power tube 12. Since waveguide section 16 is always in front of high power tube 12, the evacuated waveguide section 16 will intercept the arc before it reaches the tube 12. If the arc is severe enough to puncture the output window of tube 12, the window 20 of the evacuated waveguide section 16 will first be destroyed thereby causing an air leak therein. This in turn will cause the filament to burn out and thereby affect an open circuit which will turn off the high power to the tube. As a result, the arc will be squelched before it can reach the output window of high power tube 12. All that is required to set the system in operation again is to replace waveguide section 16, a much simpler and less expensive means than replacing the tube 12 if its output window were punctured. The size of the filament wire and potential to be used is determined by the time required to remove the high power from the circuit. An alternative to the filament 26 may comprise a suitable vacuum sensing device capable of microsecond operation.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An apparatus for protecting a high power tube in a waveguide system against damage by arcing, said tube being normally activated by a source of operating voltages, including for insertion in the system a section of evacuated waveguide terminated at each end by sealed RF windows, one of said windows coupled to the output of said high power tube, and protective response means within said waveguide-section and in circuit with said operating voltage source, said means being responsive toan arc discharge occurring in said system such that said operating volt-age source is disconnected from said power tube.

2. The apparatus in accordance with claim 1 wherein said waveguide section is rectangular in cross section, and said protective response means comprises a filament wire loop having its ends extending through the top wall of said waveguide section, and means for energizing said filament loop.

3. The apparatus in accordance with claim 1 wherein UNITED STATES PATENTS 2,498,719 2/1950 Spencer 333-17 2,546,500 3/1951 Hall. 2,833,965 5/1958 Baker 317-51 2,860,244 11/1958 Crowley 317-51 XR 2,993,181 7/1961 Friedman et al. 331-62 XR FOREIGN PATENTS 894,860 4/ 1962 Great Britain.

W. M. SHOOP, JR., Primary Examiner US. Cl. X.R. 

